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H. Y. HALL.

ELECTRIC BOOSTER. SYSTEM.

APPLICATION man APR. 24. ms.

Patented Dec. 9, 1919.

. I I I I l I l I I I l l I I I J INVENTOR H. Y. HALL H15 ATTORNEYS I o "Q WITNESSES:

HARRY Y. HALL, OF SAN FRANCISCO, CALIFORNIA.

ELECTRIC BOOSTER sYsTEM.

Specificationof Letters Patent.

Patented Dec. 9, 1919.

."Application filed April 24, 1916. Serial No. 93,062.

all whom it may concern:

Be i nown th I, TI Yv HALL, a citizen of the United States, and a resident of the city and county of San Francisco, Sta e of Ca ifo n a, hav e ed it Certain new' and useful Electric Booster System, of hic he fol ow ngs a sp cifi i =Tl e "inven ion elates to el ic booster Systems f r se Par ic larly in m s rack drepsi an pet n el di fer e in e i railw y an 'Qtherelett'rie cir Au bi i Qt he invent o is to Provide ean f r au omatic l y o r ll g track drop and, potent al di e en e in t a k r um; or othe r rn ele tr c c r Another o jec of he inven o is to P vide means forovercoming the limitations of theordinaiy series booster system.

Another object of theinvention is to provide a'boost'er system which operates to hold the difierence'in potential between two distantly spaced points on the rail or feeder t lev alue than i ipossibl t y a her t fo e u ed- Th n ention p se es oth e d en segue fea s some of hich, h e f g'oing', will beset forth at length in the following description, where I shall outline in full t f m of t e n ention h c I have selected for illustration'in the drawing accompanying and forming part-of the present specification- In said" drawing I have shown one specific form of my generic invention, but it is tobe-und'erstood that I do not limit myself tosuch form, because the invention as expressed in the succeeding claims may be embodied in a multiplicity of forms.

The drawin is a dia rammatic representation of one form of-tiesystem of my invention.

To. 7 limit the liability to electrolysis of water and gas pipes, regulations have been adopted in many communities which restrict the potential drop in the track-return circuit of electric railways to a certain maximum, and these regulations are complied with by the installation of heavy track-return feeders and track-return boosters. These booster systems have usually been of the ordinary series booster type, which systems have certain inherent short-comings and limitations, which render them unsuitable for conditions of operation wherein a very low potential difference is required between two distantly spaced points on the feeder or rail.

Under varying conditions of traflic, and w1thout the use of a booster system, the differencein potential between two distantly spaced points on the rail varies to a great extent and when a booster system is employed, the booster voltage should vary equally and oppositely in the same degree, so that the difference in potential is maintainedbelow a certain n aximu 'n. This requires a booster having awide range of voles egula n, r ro t m ximum and for t s p p I mpldy t separ t ly e c-ited booster. In many instances it impossible to obtain the desiredvoltage variation with the use of a sin le exciter with suflicient rapidity and stabi ity to meet the demands of many conditions. In accordance with my invention, I prefer toemploy a boosterand two exciters of diii'ercn't non mal voltages, connected ino position so that the resultant voltage is the voltage impressed upon the booster field winding. The low voltage eXciter preferably operates at a constant voltage and the higher voltage eXciter, which is connected in opposition, operates at a variable voltage, which is controlled by a voltage regulator.

In the drawing, the rail or feeder 2 is shown as running from a point A. to a distant point B, and the booster feeder 3, con taining the suitably driven shunt wound, separately excited, booster or generator t, is connected to the rail or feeder 2 at these two points. The booster field 5 is supplied by the two eXciters 6 and 7 connected in opposition, so that the field voltage is equal to the difference in voltage of the two exciters. The normal booster voltage is equal to the difference between the normal voltages of the eXciters. The exciter 6, which is the low voltage eXciter, operates at a substantially constant voltage and may be a generator, a battery or some other source of substantially continuous voltage. The exciter 7 is the higher voltage exciter and operates at a variable voltage. Since the two exciters are connected in opposition, when their voltages are the same, the resultant is zero voltage and no current flows into the booster field, but when the variable voltage is higher than the constant voltage, current flows into the booster field, causing the generation of voltage in the booster armature which draws the return current back to the sub-station through the booster feeder 3 instead of through the negative feeder orrail 2. The

voltage of the booster and the size of the booster feeder are so chosen, that when the cuit of the control wire 9, connected to the rail 2 at the two points A and B. The Tirrill regulator shown is of slightly modified form, so that it regulates for and to hold practically zero volts instead of a definite voltage, as ordinarily. To accomplish this result, the control element of the regulator is formed of two coils 12 and 13, the coil 12 being connected across the constant voltage exciter 6 and the'coil 13, which is the true control 'coil,- is connected in series in the control wire 9. The pull of these two coils will be in the same or in opposite directions, depending upon whether point B is at a lower or a higher otential than point A.

In one booster and regulator system which I have designed,in which opposed exciters are used, I have provided a separately excited 125 volt shunt booster and have provided a constant voltage 125 volt exciter and a variable voltage exciter connected in opposition thereto having a maximum volta e of 250volts. By varying the voltage 0 the second exciter between 125 volts and 250 volts, the voltage of the booster field is varied from zero to 125 volts, and by this arrangement, this range of voltage is obtained with greater rapidity and stability than would be possible with a single 125 volt exciter whose voltage must be varied from zero to 125 volts. Y

I claim:

1. In an electric booster system, a separately excited booster having a field winding, an exciter connected across said winding, a conductor towhich said booster is connected at distantly spaced points and means operative by variations in the potential difference of said two points for varying the exciter voltage.

2. The combination with an electric con- I ductor, of a booster circuit connected thereto at two distantly spaced points, a booster in said circuit having a field winding, an exciter connected across said winding, a control wire connecting said spaced points and a regulator in the control wire circuit connected to said exciter and adapted to contral the voltage thereof.

3. The combination with a track-return conductor of a booster circuit connected thereto at distantly spaced oints, a booster in said circuit having a fie d winding, two exciters connected in opposition and supplying said field winding and means operative by variations in the potential difference of said two points for varying the voltage of one of said ex'citers. a

4. The combination with an electric conductor, of a booster circuit connected there: to at two distantly spaced in said circuit having a fie d winding, two exciters of different normal voltage connected in op osition connected across said winding, the ower voltage exciter having a substantially constant voltage and means operative by variations in the potential difference between said spaced points for varying the voltage of the higher potential exciter.

5. The combination-with an electric conints,abooster ductor, of a booster circuit connected thereto at two distantly spaced points, a booster in.

said circuit having a field winding, two eh,-

citers of difierent normal voltage connected in opposition connected across said winding,v the lower voltage exciter having a substah-' tially constant voltage, a control wire con nectmg said spaced points and a regulator in the control wire circuit connected in series with the field of the hi her voltage exciter whereby variations in t e potential differ" ence between said spaced points varies the voltage of said higher voltage exciter.

6. he combination with an electric conductor, of a booster circuit connected there:

to at two distantl spaced points, a booster in said circuit an means for automatically vary' the potential of the booster whereby the v0 tages at said two points are main tained substantially equal.

In testimon whereof, I have hereunto setmy hand at an Francisco, California, this. 15th day of April, 1916.

HARRY Y. HALL.

In presence of H. G. Pnos'r. 

